1. Field of the Invention
The present invention relates to a gasket.
More particularly, the present invention relates to a gasket for a case which is made of a material having a low rigidity such as a synthetic resin, an aluminum or the like, and is used in an electronic equipment or the like.
2. Description of the Conventional Art
Conventionally, in a case cover of an electronic equipment or the like which is formed by a material having a low rigidity such as a synthetic resin or the like, in the light of a reservation of a sealing performance with respect to a suppression of deformation of the cover and a dispersion of a dimensional precision at a time of fastening (a tracking with respect to a partial dispersion of an amount of compression), it is often the case that a gasket having a low reaction force property and having a small rate of change of a reaction force with respect to an amount of compression is employed.
As this kind of gasket, as shown in FIG. 11, there has been known a structure constructed by a body section 310 which is inserted to a mounting groove (not illustrated), two rows of support protrusions 320 and 330 which are provided in a bottom portion side of the body section 310 and extend in parallel to the body section 310, and a lip protrusion 340 which is provided in another side of the body section 310.
Further, an air gap 350 is provided in a bottom portion side of the mounting groove in an opposite surface to the lip protrusion 340, thereby forming a shape which buffers a compression of a rubber-like elastic member (Japanese Unexamined Utility Model Publication No. 62-108661).
However, even in the gasket 300 having the shape mentioned above, it has not been a gasket having an acceptable low reaction force, with respect to the case which is made of the material having the low rigidity such as the synthetic resin, the aluminum or the like, and is used in the electronic equipment or the like.
Consequently, a gasket 300 having a shape shown in FIG. 12 has been proposed (Japanese Unexamined Patent Publication No. 2004-39341).
In other words, the gasket 300 is constructed by a body section 310 which is inserted to a mounting groove 110 of a case (one member) 100, and a lip protrusion 340 which is provided in another side of the body section 310, and the lip protrusion 340 is formed as a shape which extends while being inclined with respect to the body section 310.
In accordance with the above-mentioned construction, as shown in FIG. 13, it is possible to expect to achieve a low reaction force of the lip protrusion 340 and improve a tracking performance at a time of being brought into pressure contact with and pinched with respect to another member 200.
However, in the lip protrusion 340 having the inclined structure mentioned above, since the lip protrusion 340 is forcedly unmolded at a time of forming and unmolding the gasket 300, there is brought about a problem that the lip protrusion 340 tends to be broken and a workability is deteriorated, in the shape in which the incline is enlarged.
On the other hand, if an angle of incline of the lip protrusion 340 is made smaller, it is hard to come to a low reaction force even if the lip protrusion 340 falls over, and a change of the reaction force with respect to the amount of compression becomes larger. Further, since it is hard to fall over in a fixed direction in accordance with an aiming, and there is a possibility that it falls over partly in a reverse direction, a reduction of a sealing performance is brought about.